An extensive benchmark exercise has been conducted on ITER with the objective to test and validate different approaches for the use of CAD generated geometry data for Monte Carlo transport calculations with the MCNP code. The exercise encompassed the generation of a
dedicated neutronics CATIA model based on available engineering CAD design data, the conversion into MCNP geometry, the verification of the converted models, and a number of calculations to compare the different approaches with regard to the performance and the
validity of the results obtained. The paper briefly reviews the different approaches and provides a detailed description of the ITER benchmark effort, its results and conclusions showing that the approaches have reached the maturity level to allow their application to real ITER design analyses. This is considered an essential step forward for neutronics analysis tools to satisfy ITER quality assurance rules.